U.S. patent application number 13/816100 was filed with the patent office on 2013-08-29 for modified catalyst supports.
This patent application is currently assigned to TOTAL RESEARCH & TECHNOLOGY FELUY. The applicant listed for this patent is Martine Slawinski, Aurelien Vantomme, Christopher Willocq. Invention is credited to Martine Slawinski, Aurelien Vantomme, Christopher Willocq.
Application Number | 20130225772 13/816100 |
Document ID | / |
Family ID | 43416488 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130225772 |
Kind Code |
A1 |
Willocq; Christopher ; et
al. |
August 29, 2013 |
MODIFIED CATALYST SUPPORTS
Abstract
A supported catalyst system comprising a coprecipitated
silica-and titania-containing support, comprising alumoxane as
acatalyst activating agent, and a metallocene, wherein the
supported catalyst system has a Ti content of at least 0.1 wt
%.
Inventors: |
Willocq; Christopher;
(Bousval, BE) ; Vantomme; Aurelien;
(Bois-d'-Haine, BE) ; Slawinski; Martine;
(Nivelles, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Willocq; Christopher
Vantomme; Aurelien
Slawinski; Martine |
Bousval
Bois-d'-Haine
Nivelles |
|
BE
BE
BE |
|
|
Assignee: |
TOTAL RESEARCH & TECHNOLOGY
FELUY
Feluy
BE
|
Family ID: |
43416488 |
Appl. No.: |
13/816100 |
Filed: |
August 16, 2011 |
PCT Filed: |
August 16, 2011 |
PCT NO: |
PCT/EP2011/064093 |
371 Date: |
April 25, 2013 |
Current U.S.
Class: |
526/64 ; 502/113;
502/118; 526/114; 526/129 |
Current CPC
Class: |
C08F 210/00 20130101;
B01J 2531/56 20130101; C08F 4/65912 20130101; B01J 31/2295
20130101; B01J 2531/49 20130101; B01J 31/1616 20130101; C08F 4/76
20130101; C08F 210/00 20130101; B01J 2531/48 20130101; B01J 2531/46
20130101; B01J 31/143 20130101; C08F 110/02 20130101; Y02P 20/52
20151101; C08F 4/025 20130101; C08F 4/65916 20130101; C08F 4/65927
20130101; B01J 31/1608 20130101; C08F 210/00 20130101 |
Class at
Publication: |
526/64 ; 502/118;
526/114; 502/113; 526/129 |
International
Class: |
C08F 4/76 20060101
C08F004/76 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2010 |
EP |
10172815.2 |
Claims
1. A supported catalyst system comprising a coprecipitated silica-
and titania-containing support comprising an alumoxane and at least
one metallocene, wherein the supported catalyst system has a Ti
content of from 0.1 wt% to 12 wt %.
2. The supported catalyst system according to claim 1 having a Ti
content of from 1 to 10 wt %.
3. The supported catalyst system according to claim 1 wherein the
metallocene is selected from formula (I) or (II):
(Ar).sub.2MQ.sub.2 (I) R''(Ar).sub.2MQ.sub.2 (II) wherein the
metallocenes according to formula (I) are non-bridged metallocenes
and the metallocenes according to formula (II) are bridged
metallocenes; wherein said metallocene according to formula (I) or
(II) has two Ar bound to M which can be the same or different from
each other; wherein Ar is an aromatic ring, group or moiety and
wherein each Ar is independently selected from the group consisting
of cyclopentadienyl, indenyl, tetrahydroindenyl or fluorenyl,
wherein each of said groups may be optionally substituted with one
or more substituents each independently selected from the group
consisting of hydrogen, halogen and a hydrocarbyl having 1 to 20
carbon atoms and wherein said hydrocarbyl optionally contains one
or more atoms selected from the group comprising B, Si, S, O, F and
P; wherein M is a transition metal M selected from the group
consisting of titanium, zirconium, hafnium and vanadium; and
preferably is zirconium; wherein each Q is independently selected
from the group consisting of halogen; a hydrocarboxy having 1 to 20
carbon atoms; and a hydrocarbyl having 1 to 20 carbon atoms and
wherein said hydrocarbyl optionally contains one or more atoms
selected from the group comprising B, Si, S, O, F and P; and
wherein R'' is a divalent group or moiety bridging the two Ar
groups and selected from the group consisting of a C.sub.1-C.sub.20
alkylene, a germanium, a silicon, a siloxane, an alkylphosphine and
an amine, and wherein said R'' is optionally substituted with one
or more substituents each independently selected from the group
comprising a hydrocarbyl having 1 to 20 carbon atoms and wherein
said hydrocarbyl optionally contains one or more atoms selected
from the group comprising B, Si, S, O, F and P.
4. The supported catalyst system according to claim 1 wherein the
metallocene is selected from (I) or (II) wherein each Ar is
selected independently from an indenyl or a tetrahydroindenyl,
preferably each Ar being the same.
5. The supported catalyst system according to claim 1 wherein the
alumoxane is an oligomeric, linear or cyclic alumoxane selected
from R--(Al(R)--O).sub.x--AlR.sub.2 (III) for oligomeric, linear
alumoxanes; or (--Al(R)--O--).sub.y (IV) for oligomeric, cyclic
alumoxanes wherein x is 1-40; wherein y is 3-40; and wherein each R
is independently selected from a C.sub.1-C.sub.8 alkyl, preferably
methyl.
6. A process for preparing the supported catalyst system according
to claim 1, comprising the following steps: a). coprecipitating
precursors of titania and silica in solution in order to generate a
gel b). aging the gel c). washing the gel to remove undesirable
salts d). drying the gel to obtain the coprecipitated silica and
titania containing support e). treating the coprecipitated silica
and titania containing support with a catalyst activating agent,
preferably alumoxane.
7. The process according to claim 1 wherein the precursor of
titania is selected from one or more of the compounds having the
general formula R.sub.nTi(OR').sub.m, (RO).sub.nTi(OR').sub.m,
wherein R and R' are the same or different and are selected from
hydrocarbyl groups containing from 1 to 12 carbon, halogens and
hydrogen, and wherein n is 0 to 4, m is 0 to 4 and m+n equals
4.
8. The process according to claim 1 wherein the precursor of
titania is selected from one or more of the group consisting of
tetraalkoxides of titanium having the general formula Ti(OR').sub.4
wherein each R is the same or different and can be an alkyl or
cycloalkyl group each having from 3 to 5 carbon atoms.
9. The process according to claim 1 wherein the precursor of silica
is selected from one or more of the group silicate salts, such as
sodium silicate, and compounds having the general formula
R.sub.nSi(OR').sub.m or (RO).sub.nSi(OR').sub.m, wherein R and R'
are the same or different and are selected from hydrocarbyl groups
containing from 1 to 12 carbon, halogens and hydrogen, and wherein
n is 0 to 4, m is 0 to 4 and m+n equals 4.
10. A process for preparing a polyolefin comprising the step of
polymerising an olefin in the presence of a supported catalyst
system according to claim 1.
11. The process according to claim 1, wherein polymerization is
carried out: in a gas phase process, preferably carried out in a
fluidized bed reactor, and/or in a slurry phase process, preferably
in one or more slurry loop reactors, more preferably in two slurry
loop reactors connected in series.
12. The process according to claim 1 wherein the polyolefin is
polypropylene and wherein the process comprises the step of
polymerising propylene in a bulk process, preferably in a loop
reactor.
13. The process according to claim 1 wherein the olefin is
ethylene, optionally copolymerised with an alpha-olefin comonomer
having from 3 to 10 carbon atoms, preferably 1-hexene; or
propylene, optionally copolymerised with an alpha-olefin comonomer
having from 4 to 10 carbon atoms or ethylene, preferably
ethylene
14. A polyolefin obtainable according to claim 1.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a supported catalyst system
comprising metallocene catalysts. The invention also relates to the
process for preparing the supported catalyst system, as well as a
polymerisation process using such a supported catalyst system.
BACKGROUND OF THE INVENTION
[0002] Metallocene catalyst systems are extensively used in a
variety of polymerisation systems, including the polymerisation of
olefins. Generally, in order to obtain the highest activity from
metallocene catalysts, it has been necessary to use them with an
organoaluminoxane activating agent, such as methylaluminoxane
(MAO). This resulting catalyst system is generally referred to as a
homogenous catalyst system since at least part of the metallocene
or the organoaluminoxane is in solution in the polymerisation
media. These homogenous catalyst systems have the disadvantage that
when they are used under slurry polymerisation conditions, they
produce polymers which stick to the reactor walls during the
polymerisation process (generally referred to as "fouling") and/or
polymers having small particle size and low bulk density which
limit their commercial utility.
[0003] Various methods have been proposed in an effort to overcome
the disadvantages of the homogenous metallocene catalyst systems.
Typically, these procedures have involved the prepolymerisation of
the metallocene aluminoxane catalyst system and/or supporting the
catalyst system components on a porous carrier (also known as a
"particulate solid" or "support"). The porous carrier is usually a
silica-containing support.
[0004] Another important consideration in the development of
metallocene catalysts is the yield of solid polymer that is
obtained by employing a given quantity of catalyst in a given
amount of time. This is known as the "activity" of the catalyst.
There is an ongoing search for metallocene catalysts and techniques
for preparing such catalysts which give improved activity for the
polymerisation of olefins. An improved activity means that less
catalyst needs to be used to polymerise more olefins, thereby
reducing the costs considerably, since metallocenes are more
expensive than Ziegler-Natta and chromium catalysts.
[0005] Several attempts have been made to titanate silica supports
for use in metallocene catalysed ethylene polymerisations.
Jongsomjit et al. (Molecules 2005, 10, 672, Ind. Eng. Chem. Res.
2005, 44, 9059 and Catalysis Letters Vol. 100, Nos. 3-4, April
2005) discloses the titanation of silicas for zirconocene catalysed
ethylene polymerisation, wherein the support is prepared according
to Conway et al. (J. Chem. Soc., Faraday Trans. J, 1989, 85(1),
71-78) using mixed supports of titania and silica mixed-oxide
supports. The increase in activity with such a support is only of
25%. Under polymerisation conditions, little morphological control
can be obtained with such a support. It is particularly difficult
to use industrially, since the porous volume, bulk density and
particle size of both the silica and titania need to be similar in
order to avoid decantation of one with respect to the other. In
addition, the interaction of the Ti with the actives sites is not
optimized. Furthermore, the zirconocene (metallocene) catalyst is
not incorporated into the mixed-oxide support, but added separately
into the polymerisation reactor in the presence of 1-hexene, thus
during polymerisation.
[0006] Fisch et al. discloses immobilization of metallocene within
silica-titania by a non-hydrolytic sol-gel method (Applied
Catalysis A: General 354 (2009) 88-101). However, the MAO is used
as a cocatalyst during the polymerisation process. The MAO and the
aluminum thereof does not form an integral part of the support,
thereby allowing the formation of large amounts of undesirable TiOH
and SiOH on the co-gel.
[0007] U.S. Pat. No. 6,395,666 B1 discloses a catalyst composition
that comprises an organometallic compound, an organoaluminum
compound, and a fluoride solid oxide compound. No alumoxane is
added to said composition.
[0008] US 2003/0232716 A1 discloses a catalyst composition that
comprises an organometal compound, an organoaluminium compound and
a treated solid oxide compound. No alumoxane is added to said
composition.
[0009] U.S. Pat. No. 5,604,170 discloses the use of titanium
compounds, in particular titanium tetrachloride, however not in
combination with metallocene and alumoxane. None of the disclosed
Solid Catalyst Components of the examples show a titania-silica
co-precipitated support comprising an alumoxane and a
metallocene.
[0010] U.S. Pat. No. 5,124,418 discloses silica, alumina or
silica-alumina inorganic oxide support that may be employed in
combination with magnesia, titania, zirconia and the like.
Alumoxanes are not incorporated into the support, but are added
separately into the reactor. There is no mention of trying to
improve catalyst activities using the presence of titanium.
[0011] EP 0 514 594 A1 discloses a catalyst precursor composition
supported on a porous carrier comprising a magnesium compound, a
zirconium compound and a titanium or vanadium compound. However,
the silica and titanium compound are not co-precipitated
together.
[0012] Thus, a new catalyst support is needed for metallocene
catalysts which can induce improved activity of the metallocene
catalyst system, particularly under industrial conditions.
[0013] An object of the present invention is to provide a new
catalyst support for metallocene catalysts to increase their
activity.
[0014] Furthermore, it is an object of the present invention to
provide a new method for polymerising olefins, preferably ethylene
and propylene, using a new supported metallocene catalyst
system.
SUMMARY OF THE INVENTION
[0015] At least one of the objects is solved by the present
invention.
[0016] The invention concerns a supported catalyst system
containing a coprecipitated silica and titania containing support,
and further comprising a catalyst activating agent, preferably an
alumoxane, wherein the supported catalyst has a Ti content of at
least 0.1 wt %.
[0017] The supported catalyst system may further comprise a
single-site catalyst, preferably a metallocene.
[0018] There is also provided a process for preparing a polyolefin
comprising the step of polymerising olefins, preferably ethylene or
propylene, in the presence of a supported catalyst system according
to the invention, preferably in the gas phase or in the slurry
phase. Optionally, in the case of ethylene polymerization, the
ethylene is copolymerised with one or more alpha-olefin comonomers
selected from C3 to C12 alpha-olefins. Optionally, in the case of
propylene polymerization, the propylene is copolymerized with one
or more alpha olefin comonomers selected from ethylene, and C4 to
C12 alpha-olefins.
[0019] The polyolefin obtainable by the process of the invention
has rheological properties suitable for many applications.
[0020] Surprisingly the catalyst support according to the invention
improves the activity of the metallocene deposited thereon, since
the interaction of the Ti within the support is optimized. It is
believed, without being bound to theory, that the titanation step
according to the invention by coprecipitation rather than simple
physical mixing of oxides, causes the titanium compound to form
Si--O--Ti--OH on the surface of the pores within the silica support
even before alumoxane (e.g. MAO) addition. Furthermore, by
coprecipitation, the titanium is introduced into the framework of
the support particles. The interaction between TiOH and SiOH is
optimized even before addition of any alumoxane. The electronic
effect of the specific Ti distribution on the catalyst grain
surface increases the metallocene catalyst system's activity as
well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 represents a comparison of the catalytic activities
of the metallocene catalyst system comprising the titanium compound
added according to the invention containing a titanium content of 2
wt % and 4 wt % according to the invention with the catalytic
activities of metallocene catalyst systems not containing any
titanium.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention relates to a process for preparing a
supported catalyst system, for preparing the catalyst system
prepared with said support and for the production of polyolefins
with said catalyst system. The support according to the invention
is particularly suitable for metallocene catalyst polymerisations,
since it increases the activity of the metallocene catalyst system
considerably.
[0023] Suitable precursors of titania and silica for the
coprecipitated support used in this invention are precursors
selected from inorganic and organic compounds of silicon and
titanium which it is subsequently convertible to silicon and
titanium oxide in the gel.
[0024] Suitable precursors of silica are, for example, amorphous
silica having a surface area of at least 150 m.sup.2/g, preferably
of at least 200 m.sup.2/g, more preferably of at least 280
m.sup.2/g, and at most 800 m.sup.2/g, preferably to at most 600
m.sup.2/g, more preferably to at most 400 m.sup.2/g and more
preferably to at most 380 m.sup.2/g. The specific surface area is
measured by N.sub.2 adsorption using the well-known BET
technique.), inorganic and organic compounds of silicon such as
halides, nitrate, sulfate, oxalate, oxides, alkyl silicates and
silicate salts (e.g. sodium silicate). The silica precursor can
also be selected from one or more of the group having the general
formula R.sub.nSi(OR').sub.m or (RO).sub.nSi(OR').sub.m, wherein R
and R' are the same or different and are selected from hydrocarbyl
groups containing from 1 to 12 carbon, halogens and hydrogen, and
wherein n is 0 to 4, m is 0 to 4 and m+n equals 4.
[0025] The supported catalyst system comprises at least 20, 40, or
50% by weight of amorphous silica. The silica-titania containing
support may also contain one or more of alumina, magnesia, zirconia
and the like.
[0026] The support of the supported catalyst system is preferably
prepared by gelification (i.e. coprecipitation) of the silica
precursor with a titanium precursor in solution.
[0027] The titanium precursor can be coprecipitated in any form
from which it is subsequently convertible to titanium oxide in the
gel. Compounds suitable include inorganic and organic compounds of
titanium such as halides, nitrate, sulfate, oxalate, alkyl
titanates, alkoxides, oxides etc. The final amount of titanium
present (the Ti content) in the supported catalyst system is at
least 0.1 wt %. The resulting supported catalyst system preferably
has a Ti content of from 0.1 to less than 60 wt %, preferably 0.1
to 25 wt %, more preferably 0.5 to 15 wt %, even more preferably 1
to 10 wt %. Most preferably, the Ti content is from 2 to 10 wt %,
or even from 3 to 10 wt %.
[0028] In another embodiment the titanium precursor is selected
from one or more of R.sub.nTi(OR').sub.m and
(RO).sub.nTi(OR').sub.m, wherein R and R' are the same or different
and are selected from hydrocarbyl groups containing from 1 to 12
carbon, halogens, preferably chlorine and fluorine, and hydrogen,
and wherein n is 0 to 4, m is 0 to 4 and m+n equals 4. The titanium
compound is preferably selected from the group consisting of
tetraalkoxides of titanium having the general formula Ti(OR').sub.4
wherein each R is the same or different and can be an alkyl or
cycloalkyl group each having from 3 to 5 carbon atoms, and mixtures
thereof.
[0029] The titanium compound(s) is more preferably selected from
alkyl titanates or titanium halides, preferably selected from e.g.
Ti(OC.sub.4H.sub.9).sub.4, Ti(OC.sub.3H.sub.7).sub.4 and
TiCl.sub.4.
[0030] The coprecipitation of the titanium precursor and the silica
precursor is preformed in solution, preferably in an acidic or
basic environment.
[0031] The coprecipitated support of the catalyst system can be
obtained using the following steps: [0032] a). coprecipitating
precursors of titania and silica in solution in order to generate a
gel [0033] b). aging the gel [0034] c). washing the gel to remove
undesirable salts [0035] d). drying the gel to obtain the
coprecipitated silica and titania containing support [0036] e).
treating the coprecipitated silica and titania containing support
with a catalyst activating agent, preferably alumoxane.
[0037] In a preferred embodiment, the coprecipitated support of the
supported catalyst system is prepared by first forming a gel by
mixing an aqueous solution of the silica precursor with a solution
of the titania precursor in a strong acid, e.g. such as sulphuric
acid, this mixing being done under suitable conditions of
agitation. The concentration of the silica-titania in the gel which
is formed is preferably in the range of between 3 to 12 wt % with
the pH of the gel preferably being from 3 to 9. A wide range of
mixing temperatures can be employed, this range being preferably
from above 0.degree. C. to around 80.degree. C.
[0038] After gelling, the mixture can be aged. This can be carried
out preferably at temperatures within the range of about 20.degree.
C. to less than 100.degree. C. Preferably, aging times of at least
10 mins are used, more preferably at least one hour are used.
[0039] Following aging, the gel is preferably agitated to produce a
slurry which is washed several times with, for example, water and
for example, with either an ammonium salt solution or dilute acid
to reduce the alkali metal content (the undesirable salts) in the
gel to preferably less than about 0.1 weight percent. While various
ammonium salts and dilute acid solutions can be employed, the
preferred ammonium salts are those, such as ammonium nitrate and
ammonium salts of organic acids, which decompose and volatilize
upon subsequent drying.
[0040] Water is removed from the gel in any suitable manner and
preferably by washing with a normally liquid organic compound which
is soluble in water, or by azeotropic distillation employing an
organic compound e.g. ethyl acetate. Remaining solvents are
preferably removed In by drying, most preferably in air, at at
least 110.degree. C., preferably at least 150.degree. C., more
preferably at least 200.degree. C. This step generally lasts for at
least 1 hour, more preferably at least 2 hours, most preferably at
least 4 hours. The drying can take place in an atmosphere of dry
and inert gas and/or air, preferably nitrogen. The drying may be
carried out in a fluidised bed.
[0041] A coprecipitated silica and titania containing support is
obtained from this method, which is used as the support for the
supported catalyst system of the invention. However, all other
known methods which are generally related to the preparation of
gels, cogels, tergels etc can be used to prepare the coprecipitated
support suitable according to the invention.
[0042] In general, the support advantageously has a pore volume of
1 cm.sup.3/g to 3 cm.sup.3/g. Supports with a pore volume of
1.3-2.0 cm.sup.3/g are preferred. Pore volume is measured by
N.sub.2 desorption using the BJH method for pores with a diameter
of less than 1000 .ANG.. Supports with too small a porosity may
result in a loss of melt index potential and in lower activity.
Supports with a pore volume of over 2.5 cm.sup.3/g or even with a
pore volume of over 2.0 cm.sup.3/g are less desirable because they
may require special expensive preparation steps (e.g. azeotropic
drying) during their synthesis. In addition, because they are
usually more sensitive to attrition during catalyst handling,
activation or use in polymerisation, these supports often lead to
more polymer fines production, which is detrimental in an
industrial process.
[0043] Usually, the particle size of the supported catalyst system
D50 is from 5 .mu.m, preferably from 30 .mu.m and more preferably
from 35 .mu.m, up to 150 .mu.m, preferably up to 100 .mu.m and most
preferably up to 70 .mu.m. D50 is defined as the particle diameter,
where 50 wt-% of particles have a smaller diameter and 50 wt-% of
particles have a larger diameter. Particle size D90 is up to 200
.mu.m, preferably up to 150 .mu.m, most preferably up to 110 .mu.m.
D90 is defined as the particle diameter where 90 wt-% of particles
have a smaller diameter and 10 wt-% of particles have a s larger
diameter. Particle size D10 is at least 2 preferably at least 5
.mu.m. D10 is defined as the particle diameter where 10 wt-% of
particles have a smaller diameter and 90 wt-% of particles have a
larger diameter. Particle size distribution is determined using
light diffraction granulometry, for example, using the Malvern
Mastersizer 2000. The particle morphology is preferably
microspheroidal to favour fluidisation and to reduce attrition.
[0044] The coprecipitated silica and titania containing support can
be stored under a dry and inert atmosphere, for example, nitrogen,
at ambient temperature.
[0045] The details and embodiments mentioned above in connection
with the process for manufacturing the catalyst support also apply
with respect to the preparation of the supported catalyst system
according to the present invention.
[0046] The coprecipitated silica and titania containing support can
then be treated with a catalyst activating agent. In a preferred
embodiment, alumoxane or a mixture of alumoxanes are used as an
activating agent for the metallocene, but any other activating
agent known in the art can be used e.g. borane compounds. The
alumoxane can be used in conjunction with the metallocene in order
to improve the activity of the catalyst system during the
polymerisation reaction. As used herein, the term alumoxane is used
interchangeably with aluminoxane and refers to a substance, which
is capable of activating the metallocene.
[0047] Alumoxanes used in accordance with the present invention
comprise oligomeric linear and/or cyclic alkyl alumoxanes. In an
embodiment, the invention provides a process wherein said alumoxane
has formula (III) or (IV)
R--(Al(R)--O).sub.x--AlR.sub.2 (III)
for oligomeric, linear alumoxanes; or
(--Al(R)--O--).sub.y (IV)
for oligomeric, cyclic alumoxanes
wherein x is 1-40, and preferably 10-20; wherein y is 3-40, and
preferably 3-20; and wherein each R is independently selected from
a C.sub.1-C.sub.8 alkyl, and preferably is methyl.
[0048] In a preferred embodiment, the alumoxane is methylalumoxane
(MAO). Generally, in the preparation of alumoxanes from, for
example, aluminum trimethyl and water, a mixture of linear and
cyclic compounds is obtained. Methods for manufacturing alumoxane
are known in the art and will therefore not be disclosed in detail
herein.
[0049] The treatment of the catalyst support with the alumoxane can
be carried out according to any known method known by the person
skilled in the art. Advantageously, the alumoxane, preferably MAO,
is mixed in an inert diluent/solvent, preferably toluene, with the
catalyst support. Alumoxane deposition preferably occurs at a
temperature between 60.degree. C. to 120.degree. C., more
preferably 80.degree. C. to 120.degree. C., most preferably 100 to
120.degree. C. The amount of MAO is calculated to reach the desired
aluminium loading.
[0050] The coprecipitated silica and titania containing support is
treated with a metallocene either during treatment with the
catalyst activating agent (1-pot method) or thereafter. Any
metallocene known in the art can be applied, including a mixture of
different metallocenes. As used herein, the term "metallocene"
refers to a transition metal complex with a coordinated structure,
consisting of a metal atom bonded to one or more ligands. The
metallocene are used according to the invention is preferably
chosen from formula (I) or (II):
(Ar).sub.2MQ.sub.2 (I);
or
R''(Ar).sub.2MQ.sub.2 (II)
wherein the metallocenes according to formula (I) are non-bridged
metallocenes and the metallocenes according to formula (II) are
bridged metallocenes; wherein said metallocene according to formula
(I) or (II) has two Ar bound to M which can be the same or
different from each other; wherein Ar is an aromatic ring, group or
moiety and wherein each Ar is independently selected from the group
consisting of cyclopentadienyl, indenyl, tetrahydroindenyl or
fluorenyl, wherein each of said groups may be optionally
substituted with one or more substituents each independently
selected from the group consisting of hydrogen, halogen and a
hydrocarbyl having 1 to 20 carbon atoms and wherein said
hydrocarbyl optionally contains one or more atoms selected from the
group comprising B, Si, S, O, F and P; wherein M is a transition
metal M selected from the group consisting of titanium, zirconium,
hafnium and vanadium; and preferably is zirconium; wherein each Q
is independently selected from the group consisting of halogen; a
hydrocarboxy having 1 to 20 carbon atoms; and a hydrocarbyl having
1 to 20 carbon atoms and wherein said hydrocarbyl optionally
contains one or more atoms selected from the group comprising B,
Si, S, O, F and P; and wherein R'' is a divalent group or moiety
bridging the two Ar groups and selected from the group consisting
of a C.sub.1-C.sub.20 alkylene, a germanium, a silicon, a siloxane,
an alkylphosphine and an amine, and wherein said R'' is optionally
substituted with one or more substituents each independently
selected from the group comprising a hydrocarbyl having 1 to 20
carbon atoms and wherein said hydrocarbyl optionally contains one
or more atoms selected from the group comprising B, Si, S, O, F and
P.
[0051] The term "hydrocarbyl having 1 to 20 carbon atoms" as used
herein is intended to refer to a moiety selected from the group
comprising a linear or branched C.sub.1-C.sub.20 alkyl;
C.sub.3-C.sub.20 cycloalkyl; C.sub.6-C.sub.20 aryl;
C.sub.1-C.sub.20 alkylaryl and C.sub.7-C.sub.20 arylalkyl, or any
combinations thereof.
[0052] Exemplary hydrocarbyl groups are methyl, ethyl, propyl,
butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl,
cetyl, 2-ethylhexyl, and phenyl.
[0053] Exemplary halogen atoms include chlorine, bromine, fluorine
and iodine and of these halogen atoms, chlorine is preferred.
[0054] Exemplary hydrocarboxy groups are methoxy, ethoxy, propoxy,
butoxy, and amyloxy.
[0055] In accordance with the present invention, a process is
provided wherein ethylene monomer is polymerised in the presence of
a bridged or non-bridged metallocene. "Bridged metallocenes" as
used herein, are metallocenes in which the two aromatic transition
metal ligands, denoted as Ar in formula (I) and (II) are covalently
linked or connected by means of a structural bridge. Such a
structural bridge, denoted as R'' in formula (I) and (II) imparts
stereorigidity on the metallocene, i.e. the free movement of the
metal ligands is restricted. According to the invention, the
bridged metallocene consists of a meso or racemic stereoisomer.
[0056] The two Ar can be the same or different. In a preferred
embodiment the two Ar are both indenyl or both tetrahydroindenyl
wherein each of said groups may be optionally substituted with one
or more substituents each independently selected from the group
consisting of hydrogen, halogen and a hydrocarbyl having 1 to 20
carbon atoms and wherein said hydrocarbyl optionally contains one
or more atoms selected from the group comprising B, Si, S, O, F and
P. If substituted, both Ar are preferably identically substituted.
However, in a preferred embodiment, both Ar are unsubstituted.
[0057] In a preferred embodiment, the metallocene used in a process
according to the invention is represented by formula (I) or (II) as
given above, [0058] wherein Ar is as defined above, and wherein
both Ar are the same and are selected from the group consisting of
cyclopentadienyl, indenyl, tetrahydroindenyl and fluorenyl, wherein
each of said groups may be optionally substituted with one or more
substituents each independently selected from the group consisting
of halogen and a hydrocarbyl having 1 to 20 carbon atoms as defined
herein; [0059] wherein M is as defined above, and preferably is
zirconium, [0060] wherein Q is as defined above, and preferably
both Q are the same and are selected from the group consisting of
chloride, fluoride and methyl, and preferably are chloride; and
[0061] and wherein R'' when present, is as defined above and
preferably is selected from the group consisting of a
C.sub.1-C.sub.20 alkylene, and a silicon, and wherein said R'' is
optionally substituted with one or more substituents each
independently selected from the group comprising a halogen,
hydrosilyl, hydrocarbyl having 1 to 20 carbon atoms as defined
herein.
[0062] In another preferred embodiment, the metallocene used in a
process according to the invention is represented by formula (I) or
(II) as given above, [0063] wherein Ar is as defined above, and
wherein both Ar are different and are selected from the group
consisting of cyclopentadienyl, indenyl, tetrahydroindenyl and
fluorenyl, wherein each of said groups may be optionally
substituted with one or more substituents each independently
selected from the group consisting of, halogen and a hydrocarbyl
having 1 to 20 carbon atoms as defined herein; [0064] wherein M is
as defined above, and preferably is zirconium, [0065] wherein Q is
as defined above, and preferably both Q are the same and are
selected from the group consisting of chloride, fluoride and
methyl, and preferably are chloride; and [0066] and wherein R''
when present is as defined above and preferably is selected from
the group consisting of a C.sub.1-C.sub.20 alkylene, and a silicon,
and wherein said R'' is optionally substituted with one or more
substituents each independently selected from the group comprising
a hydrocarbyl having 1 to 20 carbon atoms as defined herein.
[0067] In an embodiment, the invention provides a process wherein
said metallocene is an unbridged metallocene,
[0068] In a preferred embodiment, the invention provides a process
wherein said metallocene is an unbridged metallocene selected from
the group comprising bis(iso-butylcyclopentadienyl) zirconium
dichloride, bis(pentamethylcyclopentadienyl) zirconium dichloride,
bis(tetrahydroindenyl) zirconium dichloride, bis(indenyl) zirconium
dichloride, bis(1,3-dimethylcyclopentadienyl) zirconium dichloride,
bis(methylcyelopentadienyl) zirconium dichloride,
bis(n-butylcyclopentadienyl) zirconium dichloride, and
bis(cyclopentadienyl) zirconium dichloride; and preferably selected
from the group comprising bis(cyclopentadienyl) zirconium
dichloride, bis(tetrahydroindenyl) zirconium dichloride,
bis(indenyl) zirconium dichloride, and
bis(1-methyl-3-butyl-cyclopentadienyl)zirconium dichloride.
[0069] In another embodiment, the invention provides a process
wherein said metallocene is a bridged metallocene.
[0070] In a preferred embodiment, the invention provides a process
wherein said metallocene is a bridged metallocene selected from the
group comprising ethylenebis(4,5,6,7-tetrahydro-1-indenyl)
zirconium dichloride, ethylenebis(1-indenyl) zirconium dichloride,
dimethylsilylene bis(2-methyl-4-phenyl-inden-1-yl) zirconium
dichloride, dimethylsilylene
bis(2-methyl-1H-cyclopenta[a]naphthalen-3-yl) zirconium dichloride,
cyclohexylmethylsilylene
bis[4-(4-tert-butylphenyl)-2-methyl-inden-1-yl] zirconium
dichloride, dimethylsilylene
bis[4-(4-tert-butylphenyl)-2-(cyclohexylmethyl)inden-1-yl]
zirconium dichloride. Ethylenebis(4,5,6,7-tetrahydro-1-indenyl)
zirconium dichloride is particularly preferred.
[0071] In another preferred embodiment, the invention provides a
process wherein said metallocene is a bridged metallocene selected
from the group comprising diphenylmethylene
(3-t-butyl-5-methyl-cyclopentadienyl) (4,6-di-t-butyl-fluorenyl)
zirconium dichloride, di-p-chlorophenylmethylene
(3-t-butyl-5-methyl-cyclopentadienyl) (4,6-di-t-butyl-fluorenyl)
zirconium dichloride, diphenylmethylene
(cyclopentadienyl)(fluoren-9-yl) zirconium dichloride,
dimethylmethylene (cyclopentadienyl)(2,7-ditert-butyl-fluoren-9-yl)
zirconium dichloride, dimethylmethylene
[1-(4-tert-butyl-2-methyl-cyclopentadienyl](fluoren-9-yl) zirconium
dichloride, diphenylmethylene
[1-(4-tert-butyl-2-methyl-cyclopentadienyl)]
(2,7-ditert-butyl-fluoren-9-yl) zirconium dichloride,
dimethylmethylene [1-(4-tert-butyl-2-methyl-cyclopentadienyl)] (3
,6-ditert-butyl-fluoren-9-yl) zirconium dichloride
dimethylmethylene (cyclopentadienyl)(fluoren-9-yl) zirconium
dichloride and dibenzylmethylene(2,7-diphenyl-3
,6-di-tert-butyl-fluoren-9-yl)(cyclopentadienyl)zirconium
dichloride.
[0072] The support is treated with the metallocene, advantageously
by mixing the desired metallocene(s) with the MAO-modified support.
Preferably mixing occurs at room temperature for a duration of at
least 15 min, preferably at least 1 hour, more preferably at least
2 hours.
[0073] In a particular embodiment, the invention provides a process
wherein the molar ratio of aluminum, provided by the alumoxane, to
transition metal, provided by the metallocene, of the
polymerisation catalyst is between 20 and 200, and for instance
between 30 and 150, or preferably between 30 and 100.
[0074] The details and embodiments mentioned above in connection
with the process for manufacturing the catalyst support and the
supported catalyst system also apply with respect to the olefin
polymerisation method according to the present invention.
[0075] The olefin polymerisation (which includes homo- and
copolymerisations) method of the present invention is preferably
carried out in the liquid phase (i.e. known as "slurry phase" or
"slurry process") or in the gas phase; or in the case of propylene
polymerisation also in a bulk process. Combinations of different
processes are also applicable.
[0076] In a slurry process, the liquid comprises the olefin, either
propylene or ethylene, and where required one or more
alpha-olefinic comonomers comprising from 2 to 10 carbon atoms, in
an inert diluent. The comonomer may be selected from one or more
alpha-olefins such as ethylene (when polymerising propylene),
1-butene, 1-hexene, 4-methyl 1-pentene, 1-heptene and 1-octene.
Preferably, the comonomer selected is ethylene if polymerising
propylene. Preferably, the comonomer selected is 1-hexene when
polymerising ethylene. In either case, the inert diluent is
preferably isobutane. Preferably, ethylene is polymerized in the
presence of a metallocene catalyst system according to the
invention in a double loop reactor, i.e, two slurry loop reactors
connected in series. In this case, an increase of 100% activity was
observed according to the invention in comparison with a
non-titanated catalyst support.
[0077] The polymerisation process for ethylene is typically carried
out at a polymerisation temperature of from 80 to 110.degree. C.
and under a pressure of at least 20 bars. Preferably, the
temperature ranges from 85 to 110.degree. C. and the pressure is at
least 40 bars, more preferably from 40 to 42 bars.
[0078] The polymerisation process for propylene is typically
carried out at a polymerisation temperature of from 60 to
110.degree. C. and under a pressure of at least 20 bars.
Preferably, the temperature ranges from 65 to 110.degree. C.,
preferably 70.degree. to 100.degree. C., more preferably 65 to
78.degree. C. and the pressure is at least 40 bars, more preferably
from 40 to 42 bars.
[0079] Other compounds such as a metal alkyl or hydrogen may be
introduced into the polymerisation reaction to regulate activity
and polymer properties such as melt flow index. In one preferred
process of the present invention, the polymerisation or
copolymerisation process is carried out in a slurry reactor, e.g.
in a liquid-full loop reactor.
[0080] The catalyst system of the invention is also particularly
suited for gas phase polymerisations of olefins. Gas phase
polymerisations can be performed in one or more fluidised bed or
agitated bed reactors. The gas phase comprises the olefin to be
polymerised, preferably ethylene or propylene, if required one or
more alpha-olefinic comonomers comprising 2 to 10 carbon atoms,
such as ethylene (when polymerising propylene), 1-butene, 1-hexene,
4-methyl-1-pentene, 1-octene or mixtures thereof and an inert gas
such as nitrogen. Preferably, the comonomer selected is 1-hexene
when polymerising ethylene. Preferably, the comonomer selected is
ethylene if polymerising propylene. In either case, optionally a
metal alkyl can also be injected in the polymerisation medium as
well as one or more other reaction-controlling agents, for example,
hydrogen. Reactor temperature can be adjusted to a temperature of
from 60, 65, 70, 80, 85, 90 or 95.degree. C. up to 100, 110, 112 or
115.degree. C. (Report 1: Technology and Economic Evaluation, Chem
Systems, January 1998). Optionally a hydrocarbon diluent such as
pentane, isopentane, hexane, isohexane, cyclohexane or mixtures
thereof can be used if the gas phase unit is run in the so-called
condensing or super-condensing mode.
[0081] Polypropylene can also be obtained by using the metallocene
catalyst system of the invention by polymerizing propylene in a
bulk process, e.g. in a loop reactor (Spheripol.RTM.) or a
continuous stirred-tank reactor (CSTR), or in a Spherizone.RTM.
process i.e. a multi-zone circulating reactor. Combinations of the
above types of processes are also applicable e.g. continuous
stirred-tank reactor (CSTR) under bulk conditions, followed by a
gas phase reactor.
[0082] Surprisingly, it was found that the supported catalyst
system according to the invention greatly improves the catalytic
activity of metallocene catalyst systems.
[0083] In one embodiment, it was found that the catalytic activity
of a metallocene catalyst system for ethylene polymerisations even
increased up to 70% by using the Ti-impregnated support according
to the invention, in comparison with a non-titanated support. In
comparison with a support impregnated with Ti having a Ti content
of over 12 wt %, the activity increased by 30 to 40%. When
polymerising ethylene, the polyethylene obtained with the catalyst
system of this invention can have a molecular weight distribution
(MWD) that is represented by the dispersion index D i.e. Mw/Mn
(weight average molecular weight/number average molecular weight,
measured by GPC analysis) of typically from 2 to 10, more typically
of 3 to 8, a density measured according to ISO 1183 typically from
0.920 up to 0.970 g/cm.sup.3 and a melt flow index (MI.sub.2)
measured according to ISO 1133, condition D, at 190.degree. C. and
2.16 kg typically from 0.1 to 50 g/10 min, preferably 0.1 to 30
g/10 min.
[0084] When polymerising propylene, the polypropylene obtained with
the catalyst system of this invention can have a density measured
according to ISO 1183 typically from 0.920 up to 0.970 g/cm.sup.3
and a melt flow index (Mb) measured according to ISO 1133,
condition L, at 230.degree. C. and 2.16 kg, in the range from 0.05
g/10 min to 2000 g/10 min.
[0085] The polyolefins obtained using the catalyst system of the
invention can be used in any application known to the person
skilled in the art.
[0086] The following Examples are given to illustrate the invention
without limiting its scope.
EXAMPLES
Supported Catalyst System "Catalyst Z1"
1. Support Modification
[0087] In a 150 mL round bottom flask, 4.0 g of TMOS
(tetramethoxysilane) and 0.28 g TNBT (titanium n-butoxide) were
added drop by drop in a 50 ml aqueous solution of H.sub.2SO.sub.4
(pH=3) stirred at 60 rpm and heated at 70.degree. C. After 2 hours,
the mixture was aged at 60.degree. C. for 24 hours. After aging,
the gel was washed with 5% ammonium nitrate solution and 5 times
with distilled water. Water was extracted from the gel by
azeotropic distillation in ethyl acetate and the remaining solvent
was removed by drying in nitrogen at 450.degree. C. for 4 h,
thereby providing the coprecipitated silica and titania containing
support.
2. MAO Treatment
[0088] 20 g of dried silica was introduced in a 500 mL
round-bottomed flask. Toluene was added and the suspension was
stirred at 100 rpm. MAO (30 wt.% in toluene) was dropwise added via
a dropping funnel and the resulting suspension was heated at
110.degree. C. (reflux) for 4 hours. The amount of added MAO was
calculated to reach the desired Al loading. After the reflux, the
suspension was cooled down to room temperature and the mixture was
filtered through a glass frit. The recovered powder was washed with
toluene and pentane before being dried under reduced pressure
overnight
3. Metallocene Treatment
[0089] In 250 mL round bottom flask, 9.8 g of the above-obtained
SMAO silica was suspended in 80 mL toluene. Then, 0.2 g of
ethylene-bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride in
a suspension of 20 mL of toluene was added to the suspended
silica-containing support. The resulting suspension was stirred at
100 rpm for 2 hours at room temperature. Finally, the obtained
catalyst was filtered, washed with toluene and pentane before being
dried overnight.
Supported Catalyst System "Catalyst Z2"
1. Support Modification
[0090] In a 150 mL round bottom flask, 4.0 g of TMOS
(tetramethoxysilne) and 0.56 g TNBT (titanium n-butoxide) were
added drop by drop in a 50 ml aqueous solution of H.sub.2SO.sub.4
(pH=3) stirred at 60 rpm and heated at 70.degree. C. After 2 hours,
the mixture was aged at 60.degree. C. for 24 hours. After aging,
the gel was washed with 5% ammonium nitrate solution and 5 times
with distilled water. Water was extracted from the gel by
azeotropic distillation in ethyl acetate and the remaining solvent
was removed by drying in nitrogen at 450.degree. C. for 4 h,
thereby providing the coprecipitated silica and titania containing
support.
2. MAO Treatment
[0091] 20 g of dried silica was introduced in a 500 mL
round-bottomed flask. Toluene was added and the suspension was
stirred at 100 rpm. MAO (30 wt.% in toluene) was dropwise added via
a dropping funnel and the resulting suspension was heated at
110.degree. C. (reflux) for 4 hours. The amount of added MAO was
calculated to reach the desired Al loading. After the reflux, the
suspension was cooled down to room temperature and the mixture was
filtered through a glass frit. The recovered powder was washed with
toluene and pentane before being dried under reduced pressure
overnight
3. Metallocene Treatment
[0092] In 250 mL round bottom flask, 9.8 g of the above-obtained
SMAO silica was suspended in 80 mL toluene. Then, 0.2 g of
ethylene-bis(4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride in
a suspension of 20 mL of toluene was added to the suspended
silica-containing support. The resulting suspension was stirred at
100 rpm for 2 hours at room temperature. Finally, the obtained
catalyst was filtered, washed with toluene and pentane before being
dried overnight.
Supported Catalyst System "Catalyst C1"
1. Support Modification
[0093] Silica support was dried under a nitrogen flow at
450.degree. C.
2. MAO Treatment
[0094] MAO was mixed in toluene with the modified support at
110.degree. C. After filtration, the recovered powder was washed
and dried overnight to obtain the MAO-modified support.
3. Metallocene Treatment
[0095] The metallocene ethylene-bis(4,5,6,7-tetrahydro-1-indenyl)
zirconium dichloride was stirred with the MAO-modified support at
room temperature for 2 hours. After filtration, the recovered
powder was washed and dried overnight to obtain the supported
catalyst system. No titanation was carried out.
Polymerisations
[0096] Polymerisations of ethylene were carried out with "Catalyst
Z1" and "Catalyst Z2" and compared with polymerisations of ethylene
using "Catalyst C1" under the same reaction conditions.
[0097] The catalyst system was injected in a 130 mL reactor
containing 75 mL of isobutane under an ethylene pressure of 23.8
bars at 85.degree. C. for copolymerization with a concentration of
2.4 wt.% hexene.
[0098] FIG. 1 shows the comparison of the catalytic activity
between the different runs, "Catalyst C1" being the comparative
example. As presented, the supported catalyst system with the
coprecipitated support according to the invention provides
increased activities. A weight percentage of only 2 wt% or 4 wt %
of Ti increased the catalytic activity by 46% and 41% respectively
compared to the Catalyst C1.
[0099] Polymerisations of ethylene were carried out with "Catalyst
Z1" and compared with polymerisations of ethylene using "Catalyst
C1" on a ADL (Advanced Double Loop) process. Catalyst Z1 showed 94%
higher catalyst activity in comparison to "Catalyst C1".
* * * * *